SPECTRAL ANALYSIS USING MASKS HAVING DIFFERENT COMBINATIONS OF TRANSMITTING AND NON-TRANSMITTING PORTIONS

• US 3,578,980 A
• Filed: 06/18/1969
• Issued: 05/18/1971
• Est. Priority Date: 06/18/1969
• Status: Expired due to Term

• Current Assignee: John A. Decker Jr, Martin O. Harwit
• Original Assignee: John A. Decker Jr, Martin O. Harwit
• Inventors: Decker, John A. Jr., Harwit, Martin O.
• Application Number:
  US04/834,392
• Time in Patent Office: 699 Days
• US Class Current: 250/237.00G
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0229 using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 3/457 Correlation spectrometry, e.g. of the intensity G01J3/453 takes precedence

Abstract

A light spectrum is projected on a photocell through a movable mask having plural combinations of arrays of light windows and opaque areas which transmit to or mask different portions of the spectral line from the photocell. The combinations of windows and opaque areas in the several arrays are different and distributed according to a set of linearly independent equations forming a matrix. As the mask is advanced stepwise the photocell successively senses all the light transmitted from the spectrum through successively interposed arrays and generates a corresponding group of values with an inverse of the mask matrix so as to derive a series of values representing the distribution of energy along the spectrum. The mask thus analyzes and encodes the spectral energy distribution.

Claims

1. Optical apparatus for sequential encoding of the value of electromagnetic energy levels distributed along a line means for imaging the line of energy levels, a photoelectric device for sensing the energy of the imaged line, optical means between the imaging means and device for selectively transmitting portions of the line to the device including a movable support having a group of arrays of energy transmitting and energy nontransmitting elements, each array having a different combination of at least two each of said transmitting and nontransmitting elements, and each array being movable with the support to a position coextensive with the line, and means for moving the support stepwise to bring the arrays sequentially to said position so that successive arrays transmit the energy from different combinations of portions of the whole line to the photoelectric device to cause the device to produce a group of electrical values each proportional to the total energy transmitted from each array, the group of values representing the energy distribution along the line.

2. Apparatus according to claim 1 wherein there are the substantially same number of arrays as there are elements in each array.

3. Apparatus according to claim 1 wherein the distribution of elements in each array is linearly independent of the distribution in other arrays.

4. Apparatus according to claim 3 wherein said distribution defines a matrix, and the aforesaid electrical values when multiplied by the inverse of the matrix directly yield the energy distribution of the line.

5. Apparatus according to claim 3 wherein the number of energy transmitting and energy nontransmitting elements in The group of arrays are substantially equal.

6. Apparatus according to claim 1 wherein the elements have substantially the same area.

7. Apparatus according to claim 1 wherein said support is curved to conform to the image plane of the line.

8. Apparatus according to claim 1 wherein said support is an elongate strip with the elements extending in a series lengthwise of the strip.

9. Apparatus according to claim 8 wherein said series of elements forms a sequence of overlapping arrays.

10. Apparatus according to claim 9 wherein said series is a series of n+ (n- 1) 1 elements, wherein n is the number of elements in each array, and n-1 is the number of overlapping elements common to successive arrays.

11. Optical apparatus for analysis and transmission of light energy distributed along a line comprising means for imaging the light line in a plane, a photoelectric device disposed to receive and sense light from the line, optical means between the imaging means and photoelectric device including an elongate strip with light transmitting and light nontransmitting elements substantially equal in number and area extending in a series lengthwise of the strip, said elements being distributed in a plurality of arrays substantially equal in number to the number of elements in each array, the elements in each array including at least two each of said transmitting and nontransmitting elements and being distributed in different combinations represented by a set of linearly independent equations defining a matrix, means for moving the strip stepwise to bring the arrays sequentially to a position coextensive with the light line so that successive arrays transmit the energy from different combinations of portions of the whole line to the photoelectric device to cause the device to produce a group of electrical values each proportional to the total energy transmitted from each array, the group of values representing the energy distribution along the line, means to register said group of values, and computer means for operating on said group of values with the inverse of the aforedefined matrix, thereby to derive a series of values displaying the distribution of light energy along said line.

12. Apparatus according to claim 11 wherein said imaging means comprises spectral dispersion optics for spreading light from a source along the line.

13. The method of recording the value of electromagnetic energy levels distributed along a line which comprises successively transmitting different combinations of portions of the line, the combination of portions transmitted being changed at each transmission and corresponding to a set of linearly independent equations, and sensing the values of energy transmitted from the line at successive transmissions to generate a group of values, each value being proportional to the total energy of each transmission.

14. The method of claim 13 characterized by operating on said group of values with the inverse of a matrix representing said set of equations, thereby to derive a series of values representing the distribution of energy along said line.